Abstract
In a symmetry-regular bar-and-joint framework of given point-group symmetry, all bars and joints occupy general positions with respect to the symmetry elements. The symmetry-extended form of Maxwell’s Rule is applied to this simplest type of framework and is used to derive counts within irreducible representations for infinitesimal mechanisms and states of self stress. In particular, conditions are given for symmetry-regular frameworks to have at least one infinitesimal mechanism (respectively, state of self stress) within each irreducible representation of the point group of the framework. Similar conditions are found for symmetry-regular body-and-joint frameworks.
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Notes
- 1.
Many published character tables for \(\mathcal{S}_{8}\) correctly assign Γ(x, y) to E 1 but also incorrectly assign Γ(R x , R y ) to E 1 instead of to E 3 [28]. The problem extends to some tables for \(\mathcal{S}_{12}\), \(\mathcal{S}_{16}\) and \(\mathcal{S}_{20}\) [1], where the correct assignment is in fact \(\varGamma (R_{x},R_{y}) = E_{(n/2-1)}\).
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Acknowledgements
This work was begun during the workshop on Rigidity and Symmetry, held at the Fields Institute, Toronto, October 17–21, 2011, and gained from discussions there with Prof. Stephen Power (Lancaster). PWF thanks the Fields Institute for financial support of his visit.
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Fowler, P.W., Guest, S.D., Schulze, B. (2014). Mobility in Symmetry-Regular Bar-and-Joint Frameworks. In: Connelly, R., Ivić Weiss, A., Whiteley, W. (eds) Rigidity and Symmetry. Fields Institute Communications, vol 70. Springer, New York, NY. https://doi.org/10.1007/978-1-4939-0781-6_7
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